The invention relates to a nozzle arrangement for applying coating material to cavities in articles, in particular vehicle bodies, having a nozzle element which may be connected to a material source, a first dispensing opening and at least one further dispensing opening through which coating material may be dispensed.
A nozzle arrangement of this kind is known for example from U.S. Pat. No. 6,554,212 B2 and is used in particular to line cavities in vehicle bodies with an anticorrosion wax. For this purpose, the nozzle element typically takes the form of an elongate nozzle lance whereof the free end has a plurality of dispensing openings. The nozzle lance is guided by means of an arm of a multiple-axis application robot and, for application, is pushed into a cavity for treatment in the vehicle body such that the region of the nozzle lance having the dispensing openings is in the interior of the cavity. Where necessary application may also be performed manually.
A vehicle body has up to 120 cavities which may have markedly differing geometries. However, it must be ensured that all the different cavities are lined with wax completely and reliably to ensure satisfactory corrosion protection. To this end, different nozzle elements are each used for different cavity types. These are adapted in respect of their shape, number and the arrangement of the respectively associated dispensing openings to a respective particular cavity type in a particular vehicle body, with the result that wax can be sprayed into the cavities at the appropriate dispensing angles and at the appropriate dispensing locations. In this case, cavities of different geometries may be associated with a cavity type. Depending on the vehicle body for treatment, up to 80 different nozzle elements may be needed for cavity protection.
So that at least a few different cavity types may be treated using one and the same nozzle arrangement, the nozzle arrangement of U.S. Pat. No. 6,554,212 B2, for example, is set up as a changeable head and includes a plurality of different nozzle elements which, as needed, are brought into an application position by means of a folding mechanism and are thereby connected to the material source.
A flowable mixture of compressed air and wax is generated, in a manner known per se, in a mixing chamber upstream of the respectively active nozzle lance and is conveyed to the dispensing openings of the active nozzle lance and there applied to the cavity through all the dispensing openings at the same time.
The mechanical construction of this kind of changeable head having a folding mechanism is very complex, however, and also relatively susceptible to disruption. For example, the nozzle elements must not be folded into position too rapidly, since a nozzle element may be bent by the momentum of abutting contact, that is to say when it takes up its application position. Moreover, the procedure of folding into place takes a relatively long time; changing from a first nozzle element to a second nozzle element typically takes 3 to 4 seconds. This restricts the number of vehicle bodies treated per unit of time and thus limits the rate of operation of the treatment plant.
Moreover, it is necessary constantly to check whether the nozzle element to be used is correctly locked in its application position and the other nozzle elements are correctly locked in their respective inactive positions. If this is not the case, there may be undesirable collisions between the nozzle elements and the vehicle body.
Further, the overall space needed for the folding mechanism is very large by comparison with the dimensions of the nozzle elements. This restricts the ability to reach cavities, in particular in the interior of the vehicle body.
During operation, the nozzle elements are soiled by wax adhering to the outside, and so have to be cleaned after a certain period of operation. For this, typically the changeable head must be removed from the robot arm and cleaned separately, at another location. So that continuous operation can be maintained even while the changeable head is being cleaned, a changeable head of the same construction, used to replace the changeable head that is to be cleaned, must be provided. This in turn has an effect on overall operating costs.
It is the object of the invention to provide a nozzle arrangement of the type mentioned at the outset which takes account of the considerations discussed above.